The present invention relates to a thermosensitive recording material, more specifically to a thermosensitive recording material improved particularly in color sensitivity.
A thermosensitive recording material generally comprises a support such as a paper, a synthetic paper, a film, etc. and a recording layer usually comprising a colorless or pale color leuco dye and a color-developing agent provided thereon, and a recording image appears instantaneously through the reaction of the leuco dye and the color-developing agent with heating.
A recorder utilizing the aforesaid thermosensitive recording material is a small sized and inexpensive, causes no noise and is easy in maintenance since it has a relatively simple structure. Also, it is extremely inexpensive in running costs as compared with an electrostatic recording system, a thermal transfer system, a stamp printing system or an ink ribbon system, and there is less fear in contaminating hands and clothes with an ink so that, in recent years, there is a great demand for recording materials such as a facsimile, a printer, a ticket machine, a label, etc. in many fields.
As properties required for a thermosensitive recording material, there are mentioned no background fog, high sensitivity to a thermal head and a thermal pen and high in color density, high in coloring initiation temperature, good in image storage stability, etc.
Of these, with regard to improvement in color sensitivity which is a particularly important property, improvements have been attempted by adding a heat-fusing substance having a relatively low melting point as a sensitizer (sensitivity improving agent) in addition to a leuco dye and a color-developing agent. For example, in Japanese Patent Publication No. 4160/1968, Japanese Patent Application Laid-Open No. 19231/1973, Japanese Patent Publication No. 17748/1974 and No. 14531/1975, Japanese Patent Application Laid-Open No. 89994/1982 and No. 82382/1985, etc., many compounds such as acetanilide, paraffin, a higher fatty acid ester, a phthalic acid ester, stearic acid amide, m-terphenyl, p-benzylbiphenyl, etc., and stearic acid amide, p-benzylbiphenyl, etc. are particularly used with a large amount.
However, accompanying with the requirement of high speed and low energy consumption to a recorder in recent years, properties are insufficient in a thermosensitive recording material using a conventional sensitizer and also there are insufficient points in properties such as background fog, coloring initiation temperature, image storage stability, etc.
The present invention has been accomplished in view of the above situation and an object thereof is to provide a thermosensitive recording material having high sensitivity and also having good other properties.